This invention is directed to a control system, and to a method of operation thereof. In particular the system comprises a plurality of control devices and at least two controllers operating on the devices in a modulating mode.
In the operation of industrial processes it is often general practice to use a single control device to provide a desired control effort function, having a single controller connected in controlling relation therewith.
In instances where an improved degree of reliability is desired it is preferable to utilize a plurality of control devices, in order to ensure redundancy, so as to improve system availability.
Thus for a given range of required control effort, utilization of at least two control devices provides the advantages of:
IMPROVED RELIABILITY, DUE TO REDUNDANCY;
A CAPABILITY OF UTILIZING SMALLER OR STANDARD CONTROL DEVICES AS OPPOSED TO SPECIALTY OR UNUSUALLY LARGE CONTROL DEVICES;
THE ACHIEVEMENT OF FINER RESOLUTION OF CONTROL IN THE CASE OF ON-OFF (BANG-BANG) CONTROL TECHNIQUES.